Question

A chemist is mixing two solutions, solution A and solution B Solution A is 15% water and solution Bis 20% water. She already has a

beaker with 10mL of solution A in it. How many mL of solution B must be added to the beaker in order to create a mixture that is 18%
water?

Answer 1

15 mL of the solution with 20% water will be needed.

Explanation:

Use the inverse relationship

10 mL * (18-15)% = x mL * (20-18)%

x = 10 mL * (3/2) = 15 mL

Answer 2

Answer: 15mL

Explanation:

Create a table. Multiply across and add down. The bottom row (Mixture) creates the equation.

Qty × % = Total

Solution A 10 15% → 0.15 10(0.15) = 1.5

Solution B x 20% → 0.20 x(0.20) = 0.20x

Mixture 10 + x × 18% → 0.18 = 1.5 + 0.20x

(10 + x)(0.18) = 1.5 + 0.20x

1.8 + 0.18x = 1.5 + 0.20x

1.8 = 1.5 + 0.02x

0.3 = 0.02x

15 = x